1. Field of the Invention
The present invention relates to a capacitance type ultrasound transducer and an ultrasound diagnostic apparatus including the capacitance type ultrasound transducer.
2. Description of the Related Art
An ultrasound diagnostic method for irradiating an inside of a body with ultrasound, converting a state of the inside of the body into an image from an echo signal of the ultrasound, and performing diagnosis is widespread. As one of ultrasound diagnostic apparatuses used in the ultrasound diagnostic method, there is an ultrasound endoscope. In the ultrasound endoscope, an ultrasound transducer is disposed at a distal end of an insertion section introduced into the body. The ultrasound transducer has a function of converting an electric signal into an ultrasound and transmitting the ultrasound to the inside of the body and receiving the ultrasound reflected in the body and converting the ultrasound into an electric signal.
In the ultrasound transducer, a ceramic piezoelectric material, for example, PZT (lead zirconate titanate) is mainly used. On the other hand, as disclosed in Japanese Patent Application Laid-Open Publication No. 2009-55474, development of a capacitance type ultrasound transducer (Capacitive Micromachined Ultrasonic Transducer; hereinafter referred to as “c-MUT”) manufactured using an MEMS (Micro Electro Mechanical Systems) technique is proceeding. The c-MUT applies a voltage between a fixed electrode and a movable electrode opposed via an insulating layer to vibrate the movable electrode and generate ultrasound. When a space between both the electrodes changes according to incident of ultrasound, the c-MUT detects a fluctuating capacitance value to detect the ultrasound.